1. Field of the Invention
The present invention relates to a printing apparatus for printing a sheet by a printhead and, more particularly, to a printing technique of conveying sheets to a printing area facing a printhead while part of a succeeding sheet overlaps part of a preceding sheet.
2. Description of the Related Art
Japanese Patent Laid-Open No. 2000-15881 describes a printing apparatus for controlling to make the marginal area of the leading edge of a succeeding sheet overlap the marginal area of the trailing edge of a preceding sheet, which comprises a feeding unit configured to separate and feed a plurality of sheets one by one, a printing unit configured to form an image on a sheet, a conveying unit configured to convey a sheet to the printing unit, a detection unit configured to detect a sheet, and a control unit configured to control driving of the feeding unit according to a signal of the detection unit.
However, the apparatus described in Japanese Patent Laid-Open No. 2000-15881 can start to feed the succeeding sheet only when the marginal amount of the trailing edge of the preceding sheet and that of the leading edge of the succeeding sheet are confirmed before the start of feeding of the succeeding sheet. This imposes a technical problem that it takes time to start to feed the succeeding sheet.
Even if the marginal amount of the trailing edge of the preceding sheet and that of the leading edge of the succeeding sheet are not confirmed, the preceding sheet and the succeeding sheet overlap each other regardless of the margins. Therefore, it is only necessary to include a determination unit configured to determine whether to convey the succeeding sheet to a position facing the printing unit while keeping an overlap state.
On the other hand, there is a printing apparatus in which the printing elements of a printhead are juxtaposed in the conveyance direction of a sheet, and which performs an image forming operation by moving the printhead in a direction perpendicular to the conveyance direction of the sheet. This printing apparatus forms an image on a sheet by a printing operation of repeating conveyance of the sheet and movement of the printhead under given conditions.
However, in the printing operation of repeating conveyance of the sheet and movement of the printhead under the given conditions, the determination unit may determine that predetermined conditions for keeping the overlap state are not satisfied. In this case, it is impossible to convey sheets while keeping the overlap state between a succeeding sheet and preceding sheet.
The present invention has been made in consideration of the above-described problem, and provides a printing technique capable of conveying printing sheets while keeping the overlap state by changing printing elements to be used so as to satisfy the predetermined conditions for keeping the overlap state.